This invention relates to measurement of straight line motion by generation of a voltage proportional to distance moved. At present, measurement similar to that accomplished by the invention is commonly performed by a Linear Variable Differential Transformer or LVDT (U.S. Pat. Nos. 2,408,524, 2,459,210, 2,461,238) and, less commonly, by magnetic devices using a variable reluctance principle (U.S. Pat. Nos. 4,121,185, 4,339,953). Practical disadvantages of the LVDT are; (a) relatively low bandwidth, that is, the proportionality of voltage to distance moved becomes insufficiently accurate for many purposes when the motion is oscillatory and above a relatively low frequency, (b) temperature sensitivity, that is, the proportionality factor relating voltage and linear movement is significantly affected by changing temperature, (c) relatively large size, since the LVDT must be longer than the required range of motion to be measured, by a factor of approximately two, (d) fragility, since the LVDT embodies three coils of fine wire which is subject to breakage under vibration or shock, and (e) relatively complex installation requiring connection to each of three internal coils. Variable reluctance devices suffer from (a) relatively poor linearity, that is, the output voltage generated is not accurately proportional to distance moved, (b) large size, and (c) temperature sensitivity. The object of the present invention is to provide a linear motion transducer and signal processor free of the above noted disadvantages, in a simple, compact embodiment suitable for such applications as robotics, automated machine tools, x-y plotters, mechanical engineering research and development, and process control.